This invention relates generally to apparatus and methods for controlling the escape of vapors from a tank being filled with a liquid and particularly to apparatus and methods for collecting vapors from a vehicle fuel tank as the tank is refilled.
It is well known that vehicle fuel tanks are among the primary sources of unburned hydrocarbon vapors in the atmosphere. Hydrocarbon vapors are a major cause of air pollution, and are generally regarded as being detrimental to the health of animals and plants. In response to these environmental problems, current state and federal legislation requires modern passenger automobiles and commercial vehicles to be equipped with a vapor recovery system for controlling evaporation of gasoline from the vehicle fuel system. Such vapor control systems typically comprise a vacuum accumulator for purging the engine of fuel vapors after the engine is turned off and an activated charcoal cannister connected to the fuel tank for scrubbing hydrocarbons from the vapors escaping therefrom.
These prior art vacuum accumulator and charcoal cannister systems function satisfactorily to control unburned hydrocarbon emissions into the atmosphere except when the filler pipe cap has been removed, as is necessary in supplying fuel, such as gasoline, to the automobile fuel tank. Proposed federal regulations would require automobiles to have a system for preventing escape of vapors from the fuel tank even when the filler cap has been removed from the filler pipe, as in supplying fuel to the tank. Large quantities of unburned hydrocarbon vapors are emitted into the atmosphere through the filler pipe as the fuel tank is being refueled. For example, if an automobile has a 25 gallon fuel tank containing only 5 gallons of gasoline then the remainder of the volume of the tank is filled with gasoline vapor. Filling the fuel tank by pumping 20 gallons of gasoline into it therefore forces 20 gallons of gasoline vapor into the atmosphere. If there were approximately 100 million automobiles in the United States, and each automobile used 20 gallons of gasoline per week, then supplying the fuel to the fuel tanks forces several hundred million tons of hydrocarbon vapor into the atmosphere per year.
Some governmental jurisdictions have required fuel pumps for supplying gasoline to automobiles to have a vapor recovery system for collecting the vapors that emanate from a fuel tank as it is being refilled. Such pumps typically have a first hose which carries gasoline to a nozzle and a second hose which carries collected vapors to a storage tank for subsequent disposal by burning. The nozzle has a fuel delivery pipe that is inserted into the automobile filler pipe. The nozzle further includes a boot or bellows-like arrangement around the fuel delivery pipe for forming a seal around the filler pipe when the delivery pipe is inserted a sufficient distance to supply fuel to the fuel tank. The nozzles are designed to be inoperative unless the seal is properly formed. As gasoline enters the fuel tank, the displaced vapor is carried through the vapor collection tube to the vapor hose. The vapor recovery nozzle is required in certain areas of Southern California and has been credited with reducing hydrocarbon emissions from automobiles in those areas.
However, the vapor recovery nozzles are heavy and awkward to operate, particularly for individuals who have little experience with such nozzles. The necessity of having a fuel delivery hose and a vapor recovery hose also contributes to the inconvenience of the vapor recovery nozzle. One of the primary concerns of the vapor recovery nozzle is that if an individual should completely fill the fuel tank, which is not recommended with such nozzles, it may be possible for liquid gasoline to be sucked into the vapor recovery line so that when the tank becomes full, gasoline exits the filler pipe through the vapor recovery line at the same rate at which gasoline enters the filler pipe through the fuel delivery pipe. The vapor recovery nozzles typically cost several hundred dollars, which is much less economical than fuel delivery nozzles found at most gasoline fuel pumps throughout the nation. The cost of the vapor recovery nozzles also causes security problems since it is impractical to remove the nozzles from fuel pumps every time a service station closes at night. Being valuable, the nozzles are often stolen.
Accordingly, there is a need in the art for an efficient, relatively inexpensive, effective apparatus and method for preventing fuel vapors from entering the atmosphere as vehicle fuel tanks are refilled.